Various devices have been used in order to dispense an inhaled metered dose of active pharmaceutical agents such as, including pressurized aerosol devices, nebulizers, pump inhalators and the like. There is growing demand for powder dispensing devices which can dispense metered doses of powdered medicament. With such devices, the powder is withdrawn by inhalation so there is less need to be concerned with synchronizing release of medication with the exact start of inspiration to insure quality of the product delivery. Additionally, dry powders may be more stable than the liquid compositions that may be found in other inhaler device forms.
The particles containing the APA that leave the DPI are desirably within a particular size range that target a specific area of the lung. If the particles containing the APA are too large, they may not enter the respiratory tract, but instead, will be deposited in the mouth or pharynx and possibly enter the digestive tract. Desirably, the DPI will deliver a consistent fine particle dose (FPD) to the targeted area of the lung.
Current dispensers may have a reservoir that holds the powder in the form of agglomerates that contain an active pharmaceutical agent. As the device is actuated, the reservoir will release a dose of agglomerates that contains the appropriate dose of the APA. After the device is actuated, the consumer inhales to force the agglomerates to be carried through inhaler flow channels and break up into a micronized powder. This micronized powder will desirably deliver a consistent dose of the APA to the targeted lung area of the consumer.
Current designs for dry powder inhalers and deagglomeration techniques are described in U.S. Pat. No. 6,240,918, U.S. Pat. No. 5,829,434, U.S. Pat. No. 5,394,868, U.S. Pat. No. 5,687,710. Swirl nozzles have been used to deagglomerate the dry powder. De-agglomeration can be achieved by introducing changes in direction in flow in a channel such that the powder is forced to strike against various channel wall sections due to the changes in direction.
Current reservoir based dry powder inhalers may not efficiently deliver a dose because the DPI may only be capable of delivering a low fine particle fraction and a low fine particle dose. If the fine particle fraction of the dose is low, then the rest of the dose may undesirably be swallowed and absorbed through the digestive tract. Additionally, the total delivered dose of APA may be limited due to the fact that only a certain total amount of powder may be dispensed from the current DPIs. Thus, it would be desirable to increase the efficiency of current DPI's to deliver a higher fine particle fraction and fine particle dose.